The invention described herein relates generally to systems for collecting and storing radiation emanating from the sun and more particularly to a novel and improved device for concentrating radiant solar energy and including a method whereby said device is used for the purpose of heating and/or cooling buildings or other structures. It is an improvement of known solar heating devices such as that of Henry Anderson, Jr., U.S. Pat. No. 3,861,379, W. C. Lee, U.S. Pat. No. 2,994,318, H. W. Caplan, U.S. Pat. No. 3,841,738, and D. E. Hervey, U.S. Pat. Nos. 3,321,012, and 3,262,493.
Current concern over the depletion of fossil fuels has renewed public interest in providing alternative energy sources. Solar energy has long been recognized as being one of the most promising sources of energy for the future. In the past a great variety of proposals have been offered for harnessing this virtually limitless and non-polluting energy source. These suggestions have ranged from huge desert solar farms to orbiting satellites beaming the sun's energy back to receiving stations on earth.
While individual solar units are presently being used in some parts of this country for heating, air conditioning and hot water, it has generally been more economical to use cheaper alternatives such as electricity or gas.. In addition to the initial cost of the solar collection equipment it has also been necessary to provide 100 percent standby capacity for use during protracted periods of bad weather. With the present incentive to conserve natural resources, past considerations in opposition to the use of solar collection equipment are no longer as impelling.
In the past, systems for utilizing solar energy have consisted, generally, of: (1) a flat-plate collector having a large glazed surface for absorbing the sun's heat, said glazed surface comprising one or more sheets of glass or a radiation-transmitting plastic film or sheet; (2) tubes or fins for conductng or directing a heat-transfer fluid from an inlet duct to an outlet and thence to an insulated storage area; (3) a metallic plate which may be flat, corrugated, or grooved, to which the tubes or fins are attached in a manner which produces a good thermal bond; (4) insulation, to minimize downward heat loss from the plate; and (5) a container or casing which holds the foregoing components and protects them. Such systems have been constructed from many different materials and in a wide variety of designs. Flat-plate collectors have been arranged in series and in parallel, and are usually deployed in large numbers together, facing south in the United States. They have been used to heat such fluids as water, water plus ethylene glycol, water plus ammonia, fluorinated hydrocarbons, air and other gases. Pumps are usually provided to circulate the heat-transfer fluid through the collector and to thereby provide space heat, hot water or air conditioning.
Several studies have shown that temperatures far above those attainable by flat-plate collectors can be reached if a large amount of solar radiation is concentrated upon a relatively small collection area. To this end, paraboloidal concentrators, similar to searchlight reflectors, have been developed to follow the apparent movement of the sun. These and other diurnal tracking devices have attained relatively high temperatures but require, in general, complicated mechanisms for their operation and can use only the direct rays of the sun, since diffuse radiation cannot be concentrated.
The principle use of concentrating collectors in the past has been in the production of steam or high-temperature fluids for use in refrigeration or power generation. The higher cost and mechanical complexity of solar concentrators which must follow the sun, and their inability to function at all on cloudy or overcast days, are disadvantages which have, in the past, discouraged their development. None of the known prior art methods and devices have incorporated the combination of features and objectives as are outlined in the following summary of the invention.